org.springframework.util.xml.XmlValidationModeDetector Maven / Gradle / Ivy
/*
* Copyright 2002-2022 the original author or authors.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* https://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.springframework.util.xml;
import java.io.BufferedReader;
import java.io.CharConversionException;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import org.springframework.lang.Nullable;
import org.springframework.util.StringUtils;
/**
* Detects whether an XML stream is using DTD- or XSD-based validation.
*
* @author Rob Harrop
* @author Juergen Hoeller
* @author Sam Brannen
* @since 2.0
*/
public class XmlValidationModeDetector {
/**
* Indicates that the validation should be disabled.
*/
public static final int VALIDATION_NONE = 0;
/**
* Indicates that the validation mode should be auto-guessed, since we cannot find
* a clear indication (probably choked on some special characters, or the like).
*/
public static final int VALIDATION_AUTO = 1;
/**
* Indicates that DTD validation should be used (we found a "DOCTYPE" declaration).
*/
public static final int VALIDATION_DTD = 2;
/**
* Indicates that XSD validation should be used (found no "DOCTYPE" declaration).
*/
public static final int VALIDATION_XSD = 3;
/**
* The token in an XML document that declares the DTD to use for validation
* and thus that DTD validation is being used.
*/
private static final String DOCTYPE = "DOCTYPE";
/**
* The token that indicates the start of an XML comment.
*/
private static final String START_COMMENT = "";
/**
* Indicates whether the current parse position is inside an XML comment.
*/
private boolean inComment;
/**
* Detect the validation mode for the XML document in the supplied {@link InputStream}.
* Note that the supplied {@link InputStream} is closed by this method before returning.
* @param inputStream the InputStream to parse
* @throws IOException in case of I/O failure
* @see #VALIDATION_DTD
* @see #VALIDATION_XSD
*/
public int detectValidationMode(InputStream inputStream) throws IOException {
this.inComment = false;
// Peek into the file to look for DOCTYPE.
try (BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream))) {
boolean isDtdValidated = false;
String content;
while ((content = reader.readLine()) != null) {
content = consumeCommentTokens(content);
if (!StringUtils.hasText(content)) {
continue;
}
if (hasDoctype(content)) {
isDtdValidated = true;
break;
}
if (hasOpeningTag(content)) {
// End of meaningful data...
break;
}
}
return (isDtdValidated ? VALIDATION_DTD : VALIDATION_XSD);
}
catch (CharConversionException ex) {
// Choked on some character encoding...
// Leave the decision up to the caller.
return VALIDATION_AUTO;
}
}
/**
* Does the content contain the DTD DOCTYPE declaration?
*/
private boolean hasDoctype(String content) {
return content.contains(DOCTYPE);
}
/**
* Determine if the supplied content contains an XML opening tag.
*
It is expected that all comment tokens will have been consumed for the
* supplied content before passing the remainder to this method. However, as
* a sanity check, if the parse state is currently in an XML comment this
* method always returns {@code false}.
*/
private boolean hasOpeningTag(String content) {
if (this.inComment) {
return false;
}
int openTagIndex = content.indexOf('<');
return (openTagIndex > -1 && (content.length() > openTagIndex + 1) &&
Character.isLetter(content.charAt(openTagIndex + 1)));
}
/**
* Consume all comments in the given String and return the remaining content,
* which may be empty since the supplied content might be all comment data.
*
This method takes the current "in comment" parsing state into account.
*/
private String consumeCommentTokens(String line) {
int indexOfStartComment = line.indexOf(START_COMMENT);
if (indexOfStartComment == -1 && !line.contains(END_COMMENT)) {
return line;
}
String result = "";
String currLine = line;
if (!this.inComment && (indexOfStartComment >= 0)) {
result = line.substring(0, indexOfStartComment);
currLine = line.substring(indexOfStartComment);
}
if ((currLine = consume(currLine)) != null) {
result += consumeCommentTokens(currLine);
}
return result;
}
/**
* Consume the next comment token, update the "inComment" flag,
* and return the remaining content.
*/
@Nullable
private String consume(String line) {
int index = (this.inComment ? endComment(line) : startComment(line));
return (index == -1 ? null : line.substring(index));
}
/**
* Try to consume the {@link #START_COMMENT} token.
* @see #commentToken(String, String, boolean)
*/
private int startComment(String line) {
return commentToken(line, START_COMMENT, true);
}
/**
* Try to consume the {@link #END_COMMENT} token.
* @see #commentToken(String, String, boolean)
*/
private int endComment(String line) {
return commentToken(line, END_COMMENT, false);
}
/**
* Try to consume the supplied token against the supplied content and update the
* "in comment" parse state to the supplied value.
*
Returns the index into the content which is after the token or -1 if the
* token is not found.
*/
private int commentToken(String line, String token, boolean inCommentIfPresent) {
int index = line.indexOf(token);
if (index > - 1) {
this.inComment = inCommentIfPresent;
}
return (index == -1 ? index : index + token.length());
}
}